Controlled circulation boiler with orifice drum



Feb. 12, 1957 w. H. ARMACOST' 1,

CONTROLLED CIRCULATION BOILER WITH ORIFICE DRUM Filed July 5, 1952 5Sheets-Sheet 1 INVENTOR.

WILBUR H. ARMACOST ATTOR Y.

Feb. '12, 1957 'w. H. ARMACOST 2,731,028

CONTROLLED CIRCULATION BOILER WITH ORIFICE DRUM Filed July 5, 1952 5Sheets-Sheet 2 INVENTOR.

WILBUR H. ARMACOST ATTOR Feb. 12, 1957 w. H. ARMACOST 2,781,028

CONTROLLED CIRCULATION BOILER WITH ORIFICE DRUM Filed July 5, 1952 5Sheets-Shget 3' 20 6/ 74 73 74 80 6O I 60 80 FIG 5 0 2617 m INVENTOR.

WILBUR H. ARMACOST BY qi a f Feb. 12, 1957 w. H. ARMACQST 2,781,028CONTROLLED CIRCULATION BOILER WITH ORIFICEI DRUM FiledLJuly 5, 1952 5Sheets-Sheet 4 INVENTOR. WILBUR H. ARMACOST ATTOR EY.

Feb. 12, 1957 v w; H. ARMACQST 8 CONTROLLED CIRCULATION BOILER WITH:ORIFICE DRUM FiledJuly 5, 1952 v 5 Sheets-Sheet 5 TOR.

' g8 70 7/ 62 "7 6 6 68 7/ 'ATTPR MACOST I CONTROLLED CIRCULATION BOILERWITH ORIFICE DRUM Wilbur H. Armacost, Scarsdale, N. Y., assignor toCombustion Engineering, Inc., a corporation of Delaware Application July5, 1952, Serial N 0. 297,267

4 Claims. (Cl. 122-406) My invention relates to steam generating meansand has specific reference to steam generators of the controlledcirculation type.

By the term controlled circulation is meant a steam generator having apositive or forced circulation through the various steam generatingcircuits and provided with means to proportion the water supply to saidcircuits. This proportioning is accomplished by means of orifices at theinlet of said various steam generating circuits.

Although this type of generator has been used extensively in Europe, andto a lesser extent in England, for nearly two decades it has not beenuntil recently that boiler manufacturers in this country have given itserious consideration. In the last few years, however, an intensivestudy of this type of unit has been carried on by the assignee of thisapplication with a finding of inherent advantages of an exceedinglypractical nature.

One of the principal reasons for the current adoption of controlledcirculation in this country is the ever increasing demand of utilitycompanies for larger and higher pressure installations.

As is well understood, so called natural circulation is motivated bymeans of the difference in density between the steam and water mixturein the steam generating tubes and the water in the downcomers. As thepressure within the boiler increases this differential in densitybecomes less and less until a point is reached at approximately 3,226pounds per square inch at which the density of steam equals that ofwater, whereupon said differential becomes zero. It is thus apparentthat for very high pressure boilers natural circulation is entirelyunsuitable and resort must be had to some type of forced circulation.

It is extremely desirable in boiler design to be able to control andproportion the distribution of water to each of the steam generatingcircuits and it is for this reason that the controlled circulation typeof boiler is being so widely chosen as the forced circulation unit mostsuitable for modern high pressure utility plants. This is pointedlyillustrated by the fact that there are now being built by or on orderwith the assignee of this application some eighteen large high pressuresteam generating units of the controlled circulation type for ninecentral station installations in this country. All of these units havebeen ordered in the last two years and range in rated output from750,000 to 1,450,000 lbs. of steam per hour (the latter being thelargest ever built to date) and design pressure from 1,670 to 2,650pounds per square inch.

In the operation of the controlled circulation unit, orifices areprovided at the entrance of each steam generating tube in order tocontrol the quantity of water flowing through said tube; with the aim ofthe boiler designer being to obtain a substantially equal circulationratio in each tube.

Circulation ratio is defined as the weight rate of water fed to thesteam generating tubes divided by the weight rate of steam generatedtherein, and ideal operation is obtained when this ratio is the same(such as 5 or some other selected value) in each steam generating tube.Since the circulation ratio will vary in accordance with the amount ofwater flowing through the tube as well as with the length of the tubeand the rate of heat absorption of the tube, it is apparent that thesefactors will govern the size of orifice required for each tube.

Heretofore, it hasbeen the practice to provide each steam generatingcircuit with an individual inlet header of cross section far too smallto admit a workman and hence requiring along its length numeroushandholes for gaining access to the individual tube orifices, astypically illustrated by the Patterson Patent No. 2,578,831, issuedDecember 18, 1951, and owned by the assignee of the instant application.A complete boiler furnace includes several (four or more) such steamgenerating circuits each of which is composed of a number of individualtubes so arranged in the furnace that all have substantially the samerate of heat absorption as well as substantially the same length. Thus,the orifice needed by each tube in a single generating circuit is of thesame size as is the orifice needed by every other tube in that circuit,wherefore all of the orifices in a single conventional inlet header areidentical.

It is a difiicult and expensive task to install the orifices in theseconventional headers since it is necessary to provide each such headerwith the numerous hand hole openings already mentioned together withmeans for closing said openings after the orifices are properlyinstalled in the individual tubes entering the header. In high pressureunits it is found that gasketed hand hole closures are unsatisfactorybecause of excessive leakage and it is necessary to weld the closureplates of these units in place. During periodic acid wash down, at whichtime it is necessary to remove the orifice, all of these hand holeclosures have to be unwelded and removed, requiring man hours intremendously large number and prolonging the period of time for whichthe unit is shut down.

It has also been the practice to arrange the .circulating system forcontrolled circulation boilers in a manner so that the water leaving aparticular region of the steam and water drum through the downcomers isreturned to the same general region of said drum through the steamgenerating tubes. Since this arrangement afiords no mixing of the boilerwater from one side of the boiler to the other, concentrations offoreign matter tend to build up at particular locations depending uponthe characteristics of the individual unit.

It is the general object of my invention to provide a controlledcirculation boiler of improved design, construction and operation thatwill :overcome the aforementioned difficulties.

A more specific object is to provide a controlled circulation boilerwith an orifice drum of suflicient cross section to permit the entranceof workmen thereinto and to establish a slow flow of circulating waterthrough the drum during boiler operation.

Another object is to provide a controlled circulation boiler with anorifice drum which serves a plurality of steam generating circuits.

A further object is to provide a controlled circulation boiler with anorifice drum and a steam and water drum interconnected in such a manneras to effect a mixing of the circulating water from one side of theboiler to the other.

Other and further objects of my invention will become apparent to thoseskilled in the art as the description proceeds.

With the aforementioned objects in view, my invention comprises anarrangement, construction and combinationembodiment that is shown by theaccompanying drawings wherein:

Fig. 1 is a vertical section of a modern high pressure, high temperaturecontrolled circulation steam generator equipped with an orifice drumlocated at the bottom of the furnace.

Fig. 2 is a sectional view taken generally along line 22 of Fig. 1showing the connection with this single orifice drum of the tubes whichconstitute the four steam generating circuits that are respectivelyidentified with the four furnace walls.

Fig. 3 is a view in the nature of a transverse section on line 33 ofFig. 2 through the orifice drum showing the circumferential dispositionof the four individual circuit rows of steam generating tubes.

Fig. 4 is a perspective view of the orifice drum and a portion of eachof the four rows of steam generating tubes connected thereto.

Fig. 5 is a view of the orifice drum (as from the lower left portion ofFig. 3) with the casing broken away to show the longitudinally disposedstrainers which cover the orifices that are provided for the four rowsof entering tubes.

Fig. 6 is an enlarged elevational view taken generally along line 6-6 ofFig. 1 showing the connection of the steam and water drum with thecirculating pumps and the connection of the pumps with the orifice drum.

Fig. 7 is a longitudinal sectional view of the orifice drum takengenerally along line 7-7 of Fig. 8 and showing further details of thestrainers earlier represented in Fig. 5.

Fig. 8 is an enlarged transverse section of the orifice drum whichcorresponds generally to the smaller representation of Fig. 3 and whichis taken on line 8-8 of Fig. 7 to show the internal construction of saiddrum (including the strainers and tube orifices) in further detail.

Fig. 9 is a sectional view taken generally along line 9--9 of Fig. 8showing the arrangement for retaining the orifices in place at the inletends of the steam generating tubes.

Fig. 10 is an elevational end view taken along line 1010 of Fig. 9showing the orifice retaining means for a number of steam generatingtubes.

Fig. 11 is an enlarged sectional view taken generally along line 11-11of Fig. 10 showing a typical mounting for the orifice at the inlet of asteam generating tube.

Fig. 12 is a sectional view showing how the tube inlet orifice of Fig.11 appears when viewed from line 12-12 with the cooperating mountingparts therefor omitted.

The illustrative steam generator benefited Referring to the drawings,wherein like parts are designated by like reference characters, the highpressure, high temperature steam generator represented by Fig. 1comprises a vertically disposed furnace 2 of generally rectangular crosssection communicating at its upper end with a horizontal gas pass 4which in turn communicates with the upper end of a vertical gas pass 6leading to air preheater 14. Furnace 2, by way of example only, is

disclosed as fired by a plurality of burners 8 that are supplied viaconduits 12 with fuel in the form of pulver ized coal from pulverizers10. Preheated air is introduced into said furnace under pressure via asuitable force draft fan (not shown) which passes the air throughprehcater 14 and ducts 16 and thence into the furnace at a plurality ofvertically spaced points; such introduction insuring complete burning ofthe fuel supplied through said burners 8.

Furnace 2 is of the water cooled type and for this purpose has its wallsas well as the floor and ceiling lined with steam generating tubes 13.In the steam generator here illustrated adjacent tubes 18 are welded oneto another (through small spacer rods not shown) to form a rigidpressure resistant metallic interior surface for the furnace; the wallor casing construction used being disclosed and claimed by co-pendingapplication Serial No.

4 317,520, filed October 29, 1952, under title of Welded Water WallConstruction. Obviously however, the invention of the presentapplication also is useable with boiler furnaces wherein the tubes 18are not so welded together but instead are organized into walls ofvarious other types and constructions.

Said steam generating tubes 18 are connected at their lower or inletends with orifice drum 20 and at their upper or outlet ends with headers22. Headers 22 are in turn connected via conduits 23 to steam and waterdrum 24 positioned adjacent the top of the furnace. A plurality ofdowncomers 25a, 25b, 25c and 25d (see Fig. 6) depend from steam andwater drum 24 and are connected at their lower ends to the inlets ofcirculating pumps 26, 27 and 28 which in turn have their outletsconnected to orifice drum 20 thereby completing a fluid circuit throughwhich the pumps are efiective to circulate the boiler water in thefollowing manner: from steam and water drum 24 downward throughdowncomers 25a, 25b, 25c and 25d, through pumps 26, 27 and 28 intoorifice drum 20, through steam generating tubes 18 into headers 22 andthrough conduits 23 back into steam and water drum 24.

The illustrative steam generator of Fig. 1 includes an economizer 29 invertical gas pass 6, a low temperature superheater 30 also positioned insaid vertical gas pass, a high temperature superheater 32 positioned inhorizontal gas pass 4 and a steam reheater 34 also positioned in saidhorizontal gas pass 4 but down stream (relative to the flow of hotcombustion gases) of said high temperature superheater 32. Economizer 29receives feed water through header 31 and is etfective to raise thetemperature of said feed water to a desired point before discharging itupwardly through tubes 29a into header 33 and thence into steam andwater drum 24 via conduits 35. Low temperature superheater 30 receives,through suitable conduits 36 and headers 38a, 33b and 380 saturatedsteam from steam and water drum 24 and discharges this steam throughconduits 40 (only one of which is shown) at a superheated temperatureinto high temperature superheater 32 where the degree of superheat isincreased to a predetermined value, after which the steam is conveyed topoints of use by suitable piping such as 42 and 44. Reheater 34receives, through conduits 46 and 48, steam from which a portion of theenergy has been removed, reheats this steam to a desired temperature andpressure and thereafter discharges it to desired points of use throughsuitable piping such as 50 and 52.

All of the foregoing heat exchange devices as well as steam and Waterdrum 24, furnace 2, including steam generating tubes 18, and orificedrum 20 are supported from above by means of suitable hangers,designated generally 54, which derive their support from buildingframework 56, preferably fabricated of steel and concrete. This methodof support reduces relative movement of the various elements of thegenerator since the direction of expansion of said elements due tochanges in temperature will be the same.

In normal operation of the generator, pumps 26, 27 and 28 are effectiveto circulate the boiler water as aforesaid. The hot gases of combustionproduced by burning of the fuel supplied by burners 8 travel upwardlywithin furnace 2 contacting the inner surface of steam generating tubes18 thereby giving up a portion of their heat to the water flowingtherethrough and converting a portion of said water into steam which iscollected in the upper portion of steam and Water drum 24 and deliveredto superheater 30. From furnace 2 the hot combustion gases passlaterally through gas pass 4 and downwardly through gas pass 6 and airpreheater 14 into a suitable stack (not shown) giving up a furtherportion of the heat contained therein to the various heat exchangedevices encountered in passage from said furnace 2 to the stack.

Some idea of the tremendous size of the boiler furnaces here dealt withmay be gained by comparing the overall height of the steam generatorshown by Fig. l with that of the workman pictured to scale at 19 (whoseheight is six feet). In this Fig. 1 installation the structural steelframework 56 has an overall height of 132 feet (equivalent to 13 storiesof an oflice building); the vertical distance between center lines ofthe lower drum 20 and the upper drum 24 is about 87 feet; and the maincombustion chamber of water walled furnace 2 has a height ofapproximately 80 feet, a depth of 22 feet from front to rear, and awidth from side to side that is dependent upon the steaming capacitydesired.

In one commercial unit now being built by applicants assignee this widthdimension is approximately 40 feet (from left wall tubes 18b to rightwall tubes 180 in Fig. 2) and the furnace is equipped with a centralwater tube partition wall (not here shown) that divides said total 40foot furnace width into two adjoining combustion chambers each of whichhas the general proportions depicted by Fig. 2. Said commercial unitinvolving the double or divided furnace just referred to (and having theother dimensions shown by Fig. 1 hereof) has a rated generating capacity(at 100% full load) of 1,055,000 pounds of steam per hour; a ratedoperating pressure of 2650 pounds per square inch; and a ratedsuperheated steam temperature of 1100 F. together with a rated reheatedsteam temperature of 1050 F.

Such cited values are obviously illustrative rather than restrictive;for as the description proceeds it will become evident that the orificedrum improvements of this invention also are useable with boilerfurnaces of other capacities, characteristics and designs.

The orifice drum 20 As previously pointed out it has been the practicein controlled circulation boilers to employ a separate inlet header foreach steam generating circuit, said headers being located adjacent thebottom of the furnace and each being relatively small wherefore numeroushand hole openings have been required to aiford access to the individualtube orifices therein. One example of this construction is illustratedin the aforementioned Patterson Patent No. 2,578,831.

Through the use of orifice drum 20 the need for these numerous headerswith their attendant limitations and disadvantages is eliminated. Saiddrum 20, here shown as composed of two semi-cylindrical shellsintegrated by welds 21 (see Fig. 8), is disposed adjacent the bottom offurnace 2 and has the tubes of all steam generating circuits of thegenerator connected thereinto. This arrangement may best be seen inFigs. 2 and 4.

Since all the tubes lining a single side of a furnace have approximatelythe same rate of heat absorption and are approximately the same lengthit will be assumed, for purposes of explanation, that these tubescomprise a steam generating circuit as hereinbefore defined. The steamgenerator of Fig. 1 when of the single combustion chamber design of Fig.2 therefore has four steam generating circuits, viz: (a) tubes 18a,lining the front wall of furnace 2, comprising one such circuit; (b)tubes 18b, lining one side wall of said furnace 2, comprising anothersuch circuit; tubes 18c, lining the other side wall, comprising thethird such circuit; and (d) tubes 18d, lining the rear wall of thefurnace, comprising the fourth such circuit.

As shown in the drawings, Figs. 3 and 4, the tubes of these fourcircuits ab-cd are connected into drum 20 in four longitudinal rowscircumferentially spaced as indicated, and in order to avoidinterference tubes 18b, 18c and 18d are first directed upwardly fromdrum 20 and then at different respective elevations (best shown by Figs.3 and 4) horizontally to their various furnace walls. Tubes 18d inextending from drum 20 to the rear wall of the furnace form a watercooled bottom for said furnace and are arranged to provide an accessopening 58 in said bottom for the extraction of ash and the like. Tubes18d and 18a are directed inwardly along the inner surface of the top offurnace 2 to approximately the center thereof at which point they areconnected to a suitable header 22, said tubes thus forming a watercooled surface for the top of the furnace.

The here disclosed connection of all of the steam generating tubes18a-bcd into the common drum 20 is accompanied by a making of said drumconsiderably larger in cross section than the customary individualheaders into which the several tube circuit groups have heretofore beenindividually connected, thereby providing sufficient space within saiddrum to maintain a relatively slow velocity of water therethrough duringoperation of the generator and to permit the entrance of workmen (one ofwhich is indicated at 19 in Fig. 1) therewithin through manholes 60provided at either end thereof (said manholes being normally closed bycovers 61). Obviously, however, the same advantages also can be realizedwhen fewer than all of the steam generating tubes 18 are connected tosaid drum 20. With workmen able to enter the drum it is unnecessary toprovide numerous handhole openings in the drum wall in order to gainaccess to the individual tube orifices 66; instead the only openingsnecessary to provide the needed access to the drum interior canadvantageously be limited to the two end manholes 60 as hereillustratively shown.

In the installation here shown this orifice drum 20 has an insidediameter of 36 inches (however diameters either smaller or larger alsomay be practicable); the wall thereof has a thickness of 3 3 inches; andeach of the end manhole openings 60 therein has a diameter of 16 inches(large enought to admit a man). The overall length of this representeddrum 20 is about 40 feet when the Fig. 1 furnace has the double chamberdesign earlier referred to and somewhat shorter when it has thesimplified single chamber design illustratively represented by Figs. 2and 4; each of the represented four tube rows 18a, 18b, 18c, 18dentering the drum includes over individual tubes 18; and each of thesetubes 18 has an inside diameter of inch and a wall thickness of inchgiving an outside diameter of 1 /2 inches. More than 400 tubes 18 (withorifices 66 therein) accordingly enter drum 20 when the Fig. 1 furnacehas the single chamber design shown by Figs. 2 and 4, and when it hasthe double chamber design earlier referred to the number of tubes 18entering this drum 20 is even larger.

Said drum 20 receives the discharge of pumps 26, 27 and 28 through aplurality of conduits 26a, 26b, 27a, 27b, 28a and 28b arranged in across-over manner (see Fig. 6), for a purpose hereinafter explained, andconveys this discharge water into the steam generating tubes 18abc--dprojecting thereinto.

The interior construction of orifice drum 20 The longitudinal rows oftubes 18a, 18b, 18c and 18d project radially through the wall of drum 20to a predetermined distance within the drum with each tube being weldedto the drum and provided at its inner extremity with a restrictor in theform of an orifice such as is shown at 66 in Figs. 11 and 12.

Referring further to Fig. 11 said inner extremity of each tube 18 iscounterbored to snugly receive annular bushing 62 therewithin whichbushing in turn receives orifice adaptor 64. Said adaptor 64 and bushing62 have passages therethrough corresponding to the passage through thesteam generating tube 18. Adaptor 64 is provided with a radiallyextending annular flange 67 inwardly of which projects a cylindricalboss 65 counterbored to receive, with a force fit, orifice member 63having an orifice 66 (see Fig. 12) of predetermined size formed therein.

As previously noted the size of the orifice 66 for each tube 18 isdetermined in accordance with a number of factors, with the aim being toobtain a substantially equal circulation ratio in all of the steamgenerating tubes that are utilized in the complete boiler. The tubecircuits 18a, 18c and 18d will therefore require orifice members 63having difierently sized openings (see Fig. 12); and in order to makecertain that each tube 18 entering the drum 20 can receive only anorifice 66 of the particular size that has been pre-selected therefor,the bushing 62 and adapter 64 identified with each individual orificesize are matched or mated in some distinctive way such as is disclosedand claimed by copending application Serial No. 313,202, filed October6, 1952, now Patent No. 2,694,385, under title of Size IdentifiedMounting Means for Flow Restricting Orifices.

In order to retain adapters 64 (with their force fitted orifice members63) in place in bushing 62 during operation of the generator, channelmembers 68, of sufficient length to span a plurality of tubes in asingle row, are suitably bored to receive the cylindrical boss 65 ofeach orifice adapter 64 in a way permitting the channel member 68 tobear against the flange 67 of each such adapter. Studs 70 (Fig. 9) arewelded to the inner surface of drum 20 intermediate certain of saidtubes 18 and pass through suitable openings provided in channel members68. Nuts 71 threadedly received on the end of studs 70 retain saidchannel members in place.

In order to prevent foreign matter that enters drum 20 from pumps 26, 27and 28 from clogging the aforementioned orifices, strainers are providedto filter out said foreign matter before it can reach the orifices. Inthe illustrative form here shown these strainers comprise two generallysemi-circular perforate members 72 and 73 extending longitudinally ofdrum 20 (see Figs. 3 and with member 72 encompassing the inlet ends ofsteam generating tubes 18c and 18b and member 73 encompassing the inletends of steam generating tubes 18a and 18d; the individual perforateopenings (see Fig. 7) in these strainer members having a diameter ofabout inch and thus being considerably smaller than the protectedopenings in tube orifices 66. Each of the perforate members 72 and 73comprises a plurality of individually shorter members (actually thirteenin the organization shown, see Fig. 5) provided with abutting flanges 74secured together with bolts 76 to form an integrated structure.

Angle members 78 are disposed longitudinally of drum and welded to theinner surface thereof. Outwardly turned flanges 79 (see Fig. 8) ofperforate members 72 and 73 overlay one leg of said angle members andare secured thereto by any suitable, readily removable, means such asbolts. End plates 80 (most clearly shown by Figs. 5 and 7) are welded tothe inner surface of drum 20 at its left and right ends and bolted tothe endmost flanges 74 of perforate members 72 and 73 thereby completingthe enclosure of the inlet ends of tubes 18a, 18b, 18c and 18d thusforcing all of the boiler water entering drum 20 via conducts 26ab,27a-b and 28ab (see Fig. 6) to pass through the small openings in saidperforated members before entering said tubes.

All of the aforesaid strainer parts are dimensioned for ready entry intoorifice drum 20 via either of the end manholes 60 and a similarstatement applies to the tube orifices 66 and mounting members therefor.

The interconnection of orifice drum 20 and steam and water drum 24 Incontrolled circulation boilers it has been the practice to provide eachdowncomer with an individual circulating pump and to have a particularpump supply a designated group of steam generating tubes throughsuitable inlet headers. This often resulted in concentration of boilerwater impurities at various horizontal locations in the boiler due tothe fact that no mixing of the circulating water from one side of theboiler to the other was provided. In the illustrative steam generator ofFig. l specific provision is made to effect a thorough mixing of thecirculating water from one side of the boiler to the other.

Downcorners a, 25b, 25c and 25d (best shown in Fig. 6) depend from steamand water drum 24 and are connected at their lower ends to manifold 82.Also connected to said manifold 82 but intermediate the connection ofeach of the downcomers therewith are the earlier mentioned pumps 26, 27and 28 with a gate valve 83 positioned in each pump connection for thepurpose of isolating the pump should such become necessary. The outletof each of the pumps 26, 27 and 28 is connected with orifice drum 20 insuch a manner that the water handled by each pump is introduced intoorifice drum 20 in substantially the reverse longitudinal location fromwhich said water was taken from steam and water drum 24.

For this purpose conduits 26a and 26b connecting the outlet of pump 26to orifice drum 20 extend to the right, as view in Fig. 6, so that thewater from pump 26, which is taken from the left end of steam and waterdrum 24 (via downcomers 25a-b), is conveyed to the right end of drum 20;conduits 27a and 27b connecting the outlet of pump 27 to orifice drum 20extend to the left and right, respectively, so that the water from pump27, which is taken from the central portion of drum 24 (via downcomers25bc) is conveyed to the left and right ends of drum 20; and conduits28a and 28b connecting the outlet of pump 28 with drum 20 extend to theleft so that the water from pump 28, which is taken from the right endof drum 24 (via downcomers 25cd) is conveyed to the left end of drum 20.Each of the conduits 26a, 26b, 27a, 27b, 28a, 28b is provided with acheck valve 84 arranged to prevent back flow through pumps 26, 27 and28. By means of this cross-over system of piping intimate mixing of thecirculating water from one side to the other side of the boiler isobtained at all times thereby insuring that there will be noconcentration of dissolved solids and other impurities at a particularhorizontal location in the boiler.

Advantages and summary From the foregoing it will be seen that I haveprovided a controlled circulation steam generator with an orifice drum20 which is of suflicient diameter to insure a relatively slow flow ofthe circulating water therethrough and to permit the entrance of workmentherewithin; and that through this arrangement I am able to obtain anumber of significant advantages over previously known types ofcontrolled circulation boilers.

Among such advantages are; provision of a settling chamber (i. e. thebottom of the orifice drum) into which suspended solids can collect inlarge quantity Without interfering with normal operation of the unit andfrom which removal can readily be effected through the dmms manholeopenings 60; insurance that the chemicals introduced into the boilerwater to treat the same have had sufficient time to react and thoroughlymix with said water before it enters the steam generating tubes;provision for better and more rapid accessibility of orifices andstrainers both as to replacement and inspection thereby improving theavailability of the generator; elimination of the welded hand holesrequired in supply headers of the prior art type; provision for a moreeconomical design of casing and insulation at the lower part of thefurnace, which installation of all tube orifices in the single drum 20makes possible; and reduction in the problem of support since the singleorifice drum 20 is easier to mount than are the numerous headerspreviously required for the various individual steaming circuits (suchas 18a, 18b, 18c, 18d).

It will further be seen that I have also provided a controlledcirculation boiler with an orifice drum interconnected with the steamand water drum in such a manner as to insure a positive mixing of thecirculating water from one side of the boiler to the other.

While I have shown and described one preferred embodiment of my orificedrum invention and have disclosed same as being applied to a controlledcirculation steam generator of a particular design it is to beunderstood that such showing and application are illustrative and notrestrictive and that variations and modifications may be made thereinwithout departing from the spirit and scope of the invention. Itherefore do not wish to be limited to the precise details set forth butdesire to avail myself of such changes and alterations as fall withinthe purview of my invention.

What I claim is:

1. In a controlled circulation boiler of the type described, a generallyvertical furnace for receiving and burning fuel; a plurality ofcontiguous steam generating tubes associated with said furnace forabsorbing heat from the fuel burned therewithin having their inletsadjacent the lower portion and their outlets adjacent the upper portionof said furnace; a generally horizontal steam and water drum into whichthe outlets of at least a majority of said tubes communicate; an orificedrum parallel to said steam and water drum and having the inlets of saidmajority of tubes connected thereto; restrictor orifices associated withthe inlets of the tubes so connected; a plurality of downcomersdepending from said steam and water drum and longitudinally displacedtherealong; and pump means fluidly connecting each of said downcomers tosaid orifice drum in substantially reverse longitudinal position withrespect to the connection of the downcomers with the steam and waterdrum, said pump means being effective to circulate water through saidorifice drum and said restrictor orifices into said tubes, through saidtubes into the steam and water drum and thence through the downcomersback into said orifice drum.

2. In a controlled circulation boiler of the type described, a generallyvertical furnace for receiving and burning fuel; a plurality of steamgenerating circuits associated with said furnace for absorbing heat fromthe fuel burned therewithin, each of said circuits comprising amultiplicity of contiguous tubes having their inlets adjacent the lowerportion and their outlets adjacent the upper portion of said furnace; agenerally horizontal steam and water drum into which the outlets of saidtubes communicate; an orifice drum having a normally closed manhole inits end for access to the drum interior, said drum being in parallelrelation to said steam and water drum and having the inlets of the tubesof a number of said circuits connected thereinto; a restn'ctor orificeassociated with the inlets of the tubes so connected; a plurality ofdowncomers depending from said steam and water drum and longitudinallydisplaced therealong; and pump means fluidly connecting each of saiddowncomers to said orifice drum in substantially reverse longitudinalposition with respect to the connection of the downcomers with the steamand water drum, said pump means being effective to circulate waterthrough said steam generating tubes into said steam and Water drum andthence through the downcomers into the orifice drum and then throughsaid orifice drum back into said steam generating tubes.

3. In a controlled circulation boiler of the type described having agenerally vertical furnace of polygonal transverse section with theinner surface of each of the sides lined with longitudinally disposedparallel contiguous tubes whereby each such side forms a separate steamgenerating circuit, a generally horizontal steam and water drum adjacentthe upper portion of said furnace and operatively connected to theoutlet ends of the tubes of each of said steam generating circuits, aplurality of downcomers depending from said steam and water drum andlongitudinally displaced therealong, and pump means for circulatingwater from each of said downcomers through said boiler, the combinationof an orifice drum adjacent the lower portion of the furnace ingenerally parallel relation to said steam and water drum and having theinlet ends of the tubes of each of said circuits connected thereinto incircumferentially spaced longitudinal rows; restrictor orificesassociated with the inlets of said tubes for restricting the flowthrough said tubes in accordance with predetermined factors; strainermeans including a plurality of elongated perforated plates fixedlysecured longitudinally within said drum in such a manner as to filterthe water flowing from the interior of said drum into and through saidrestrictors; and means fluidly connecting said pump means to saidorifice drum in such a manner that water flowing from a particularlongitudinal location of the steam and Water drum through a particulardowncomer enters the orifice drum at substantially the reverselongitudinal location thereby mixing the circulating water from one sideof the boiler to the other, said pump means being effective to circulatethe water through the steam generating tubes into the steam and waterdrum, thence through the downcomers into the orifice drum and thenthrough the strainer plates and orifices back into the steam generatingtubes.

4. In a controlled circulation boiler, a plurality of steam generatingcircuits each of which is composed of a multiplicity of tubes; anorifice drum having a normally closed manhole in its end for access tothe drum interior, said drum having the inlets of a number of said tubesassociated therewith in a plurality of longitudinal rows along the drumwall; an orifice associated with each such inlet; means for establishinga forced circulation of boiler water through said drum, said orifices,said steam generating circuits and thence back into said drum; strainermeans within said drum disposed between the inlet for boiler water intosaid drum and said inlets of said number of tubes effective to filterthe boiler water prior to passage through the orifices, said strainermeans comprising a plurality of perforate plates individually admissiblethrough said manhole and assembled within the drum in end-to-endabutting relation so as to form a continuous elongated strainerextending longitudinally of the drum throughout substantially its entirelength with said strainer encompassing the said orificed tube inlets insaid plurality of tube rows, said perforate strainer plates removablysecured to the inner surface of the drum and to abutting strainer platesthereby providing ready access to a particular orifice.

References Cited in the file of this patent UNITED STATES PATENTS1,988,659 La Mont Jan. 22, 1935 2,357,300 Bailey Sept. 5, 1944 2,578,831Patterson Dec. 18, 1951 FOREIGN PATENTS 223,858 Great Britain Feb. 19,1925 414,896 Germany June 16, 1925 427,783 Germany Apr. 14, 1926 535,959Germany Oct. 17, 1931 450,114 Italy July 8, 1949 651,048 Great BritainMar. 7, 1951

